Question

A whistler of frequency $540Hz$ rotates in a circle of radius $2m$ at an angular speed of $15rad/sec$. What is the lowest and highest frequency heard by listener? $\left( take{ V }_{ sound } = 330m/sec\right)

• A. $540,330$
• B. $495,540$
• C. $495,594$
• D. $samealways$

Answer 1

The correct option is C $495,594$

$\begin{array}{c}V=r\omega \to \text{for circular motion}\\ V_s=2\times 15=30\end{array}$

$\begin{array}{c}\text{frequency is min at}B\text{and}max\text{at}D\\ \begin{array}{c}fmin=f\left(\frac{v}{v+v_s}\right)=540\times 330\\ \mathrm{fmax}=f\left(\frac{v}{v-v_s}\right)=540\times 330\\ 330-30\end{array}=594tz\\ \text{Hence option}c\text{is correct}\end{array}$